1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive employing a disk command data structure for tracking a write verify status of a write command.
2. Description of the Prior Art
It has been suggested to perform a write verify operation in a disk drive in order to verify the recoverability of recently written data before the write data is purged from the cache buffer. If a write-verify fails, the write command is typically re-executed and re-verified. If the write verify fails a number of times, the marginal data sector is typically relocated.
The cache buffer typically comprises a valid queue for caching read data read from the disk, a dirty queue for buffering write data to be written to the disk, and an available queue for buffering the write data after it has been written to the disk. The write data in the available queue is typically de-allocated for use by new commands prior to de-allocating read data from the valid queue or flushing write data from the dirty queue. However if a write verify policy is implemented, it is necessary to verify a write command before purging the write data from the cache buffer.
There is, therefore, a need to track the status of write data in a disk drive so that it is not purged from the cache buffer until passing a write verify operation.